A 6-amino-acid synthetic peptide and the most potent growth hormone releasing peptide ever developed. Produces the largest GH release of any GHRP. Uniquely, hexarelin also binds to cardiac CD36 receptors, providing GH-independent cardioprotective effects that have generated significant research interest.
Hexarelin (His-D-2-MeTrp-Ala-Trp-D-Phe-Lys-NH2), also known as examorelin, is the most potent synthetic growth hormone releasing peptide. It produces greater GH release per dose than GHRP-6, GHRP-2, or ipamorelin.
What makes hexarelin unique among GHRPs is its binding to CD36 receptors in cardiac tissue — an interaction independent of the ghrelin receptor. This CD36 binding provides cardioprotective effects (anti-fibrotic, anti-apoptotic in cardiomyocytes) that persist even after GH receptor desensitization occurs.
Hexarelin is the most potent GH-releasing peptide in the GHRP family — it produces the largest GH pulse per dose of any synthetic secretagogue. However, its clinical utility is limited by two factors: it produces the most pronounced cortisol and prolactin elevations of any GHRP, and it exhibits significant tachyphylaxis (loss of effect with repeated dosing). GH response typically diminishes substantially within 2-4 weeks of daily use, making it unsuitable for long-term protocols.
What makes hexarelin scientifically interesting beyond its GH effects is its interaction with the cardiac CD36 receptor (cluster of differentiation 36). CD36 is a scavenger receptor involved in fatty acid uptake in cardiac muscle cells. Hexarelin binding to cardiac CD36 has been shown to produce cardioprotective effects in preclinical models — including protection against ischemia-reperfusion injury and reduction of cardiac fibrosis — independent of its GH-releasing activity. This cardioprotective mechanism is unique among GH secretagogues and has generated interest in hexarelin as a potential cardiac therapeutic, though clinical development for this indication has not advanced significantly.
Hexarelin's dual receptor mechanism distinguishes it from all other GHRPs. The GHS-R1a interaction produces the most potent GH release of any secretagogue, but this same potency leads to receptor desensitization with repeated dosing (GH response diminishes over 4-8 weeks). The CD36 interaction does not desensitize, providing sustained cardioprotective effects even when GH release has attenuated.
| Pathway | Effect | Significance |
|---|---|---|
| Maximum GH release | Most potent GHS-R1a agonist known | Greatest peak GH levels of any GHRP |
| CD36 cardiac binding | Activates cardioprotective pathways independent of GH | Anti-fibrotic, anti-apoptotic effects on cardiomyocytes |
| GHS-R1a desensitization | Receptor downregulation with chronic high-potency stimulation | GH-releasing effect diminishes over 4-8 weeks of continuous use |
| Cortisol/prolactin | Significant HPA axis stimulation | Comparable to GHRP-6; less selective than ipamorelin or GHRP-2 |
| Anti-fibrotic | Reduces cardiac fibrosis via CD36-PPARgamma pathway | May benefit heart failure and post-MI remodeling |
| Study | Design | Findings | Level |
|---|---|---|---|
| GH potency | Clinical comparison | Hexarelin produced greater GH area-under-curve than GHRP-6, GHRP-2, and ipamorelin at equivalent doses | Level II |
| Cardiac protection | Preclinical + Phase II | Improved cardiac function in animal MI models. Human Phase II showed improved cardiac parameters in GH-deficient patients. | Level II |
| CD36 mechanism | In vitro + in vivo | Cardioprotective effects persisted even when GHS-R1a was blocked, confirming CD36-dependent mechanism | Preclinical |
| Desensitization | Clinical observation | GH release diminished by 50-70% after 4-8 weeks of daily hexarelin administration | Level II |
Cortisol and prolactin: Hexarelin produces the largest cortisol and prolactin elevations of any GHRP, which limits its utility for chronic use. Single doses produce transient but significant spikes in both hormones.
Tachyphylaxis: The most clinically significant limitation: hexarelin's GH-releasing effect diminishes rapidly with repeated dosing, typically within 2-4 weeks. This makes it impractical for the sustained GH elevation protocols used in anti-aging medicine. Some clinicians use hexarelin in short cycles (2-4 weeks on, 2-4 weeks off), but this approach has not been validated in clinical trials.
Cardioprotective potential: The CD36-mediated cardiac effects are generally considered beneficial, though the clinical significance of these effects at standard GH-secretagogue doses is not established.
| Jurisdiction | Status |
|---|---|
| FDA | Not approved |
| WADA | Banned under S2 |
| Research | Primarily of interest for cardiac applications (CD36 pathway) rather than GH optimization |